1. Field of the Invention
The present invention relates to an actuator as a micro-mechanical structure to which micromachining technology is applied, for use in e.g. optical scanning apparatuses for use in laser printers and the like, reading apparatuses such as bar-code readers, laser projectors, and so on.
2. Description of the Related Art
In an actuator formed by micromachining technology, for example, a movable section may be supported by hinges, such that the movable section is allowed to move due to electrostatic attraction occurring between the movable section and an electrode opposing the movable section, where the hinges serves as an axis.
As compared to conventional mechanical structures, such an actuator formed by micromachining technology has a simple structure and permits semiconductor batch processing, and therefore can be easily downsized and enable reduction of production cost. Thus, a drastic performance improving effect can be expected.
Japanese Laid-Open Patent Publication No. 2004-341364 discloses a mono-axial pivoting type oscillating mirror device in which electrostatic attraction is generated also at the walls of a mirror section, thus to minimize deformation of the mirror section during pivoting.
Japanese Laid-Open Patent Publication No. 2005-205577 discloses a mono-axial pivoting type mirror device in which electrostatic attraction is generated symmetrically with respect to an axis which is orthogonal to the pivot axis, thus to ensure stable operation.
In applications which require scanning over a broad range, e.g., scanning mirror devices for image display apparatuses or scanning mirror devices for image capturing, obtaining a large displacement of the movable section has resulted in the following problems.
A possible method for realizing a large displacement of the movable section might be to increase the electrostatic attraction which serves as a driving force, or reduce the spring modulus of the hinges. However, either method will result in the problem of a deteriorated driving stability.
Another method, which involves use of electrostatic attraction to ensure stable operation, has a problem in that balance may be lost when the movable section makes a large displacement, thus resulting in a deteriorated driving stability.